U.S. patent application number 17/426518 was filed with the patent office on 2022-04-28 for method for obtaining a substrate coated with a functional layer.
The applicant listed for this patent is SAINT-GOBAIN GLASS FRANCE. Invention is credited to Nicolas DESBOEUFS, Lucie DEVYS, Arnaud HUIGNARD, Laurent MAILLAUD, Emmanuel MIMOUN, Jean-Philippe SCHWEITZER.
Application Number | 20220127190 17/426518 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-28 |
United States Patent
Application |
20220127190 |
Kind Code |
A1 |
DESBOEUFS; Nicolas ; et
al. |
April 28, 2022 |
METHOD FOR OBTAINING A SUBSTRATE COATED WITH A FUNCTIONAL LAYER
Abstract
A process for obtaining a material including a substrate coated
on one of its sides with a coating including a functional layer,
includes depositing the functional layer on the substrate, then
depositing an absorbent layer on top of the functional layer, then
performing a heat treatment by radiation, the radiation having at
least one treatment wavelength between 200 and 2500 nm, the
absorbent layer being in contact with air during the heat
treatment, wherein the ab sorb ent layer ab sorbs at least 80% of
the radiation used during the heat treatment and transmits less
than 10% thereof.
Inventors: |
DESBOEUFS; Nicolas;
(COMPIEGNE, FR) ; SCHWEITZER; Jean-Philippe;
(CHAMANT, FR) ; HUIGNARD; Arnaud; (COMPIEGNE,
FR) ; MAILLAUD; Laurent; (MASSY, FR) ; DEVYS;
Lucie; (PARIS, FR) ; MIMOUN; Emmanuel;
(BOULOGNE-BILLANCOURT, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAINT-GOBAIN GLASS FRANCE |
COURBEVOIE |
|
FR |
|
|
Appl. No.: |
17/426518 |
Filed: |
January 28, 2020 |
PCT Filed: |
January 28, 2020 |
PCT NO: |
PCT/FR2020/050124 |
371 Date: |
July 28, 2021 |
International
Class: |
C03C 17/36 20060101
C03C017/36; C09D 133/08 20060101 C09D133/08; C08K 3/04 20060101
C08K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2019 |
FR |
1900793 |
Claims
1. A process for obtaining a material comprising a substrate coated
on one of its sides with a coating comprising a functional layer,
said process comprising: depositing the functional layer on the
substrate, then depositing an absorbent layer on top of said
functional layer, then performing a heat treatment by radiation,
said radiation having at least one treatment wavelength comprised
between 200 and 2500 nm, said absorbent layer being in contact with
air during the heat treatment, wherein the absorbent layer absorbs
at least 80% of the radiation used during the heat treatment and
transmits less than 10% thereof.
2. The process as claimed in claim 1, wherein the absorbent layer
comprises at least 5% by weight of a radiation-absorbing agent.
3. The process as claimed in claim 1, wherein the absorbent layer
comprises a radiation-absorbing agent dispersed in an organic
matrix.
4. The process as claimed in claim 3, wherein the organic matrix is
based on a polymer which is soluble in water, dispersible in water
and/or eliminable by thermal decomposition at least in part during
the heat treatment.
5. The process as claimed in claim 3, wherein the organic matrix is
based on acrylate polymer.
6. The process as claimed in claim 3, wherein the absorbent layer
has a thickness of 1 to 50 .mu.m.
7. The process as claimed in claim 1, wherein the absorbent layer
comprises at least 50% by weight of a radiation-absorbing
agent.
8. The process as claimed in claim 7, wherein the absorbent layer
has a thickness of 0.5 to 5 .mu.m.
9. The process as claimed in claim 1, wherein the
radiation-absorbing agent is selected from carbon particles.
10. The process as claimed in claim 1, wherein the radiation is
selected from laser radiation, radiation from an infrared lamp or
radiation from a flash lamp.
11. The process as claimed in claim 1, wherein the process is
devoid of a washing step between the heat treatment and a
subsequent storage of the coated substrate.
12. A material comprising a substrate coated on at least one of its
sides with a coating comprising a functional layer and an absorbent
layer located above the functional layer, wherein the absorbent
layer comprises at least 5% by weight of carbon particles.
13. The process as claimed in claim 4, wherein the polymer is
selected from polymers comprising one or more starch homopolymers
or copolymers, casein, acrylates, acrylamide, glycols, vinyl
acetate, vinyl alcohol, vinyl pyrrolidone, styrene/acrylic acid
copolymers, ethylene/acrylic acid copolymers, and cellulose or
derivatives thereof.
14. The process as claimed in claim 13, wherein the glycol is
ethylene glycol.
15. The process as claimed in claim 5, wherein the acrylate polymer
is obtained by polymerization of (meth)acrylate compounds selected
from monomers, oligomers, prepolymers or polymers comprising at
least one (meth)acrylate function.
16. The process as claimed in claim 9, wherein the carbon particles
are particles of carbon black, graphite, graphene, carbon
nanotubes, or mixtures thereof.
Description
[0001] The invention relates to the obtaining of substrates coated
with at least one functional layer.
[0002] Some functional layers require heat treatments, either to
improve their properties or even to give them their functionality.
By way of example, mention may be made of low-emissivity functional
layers based on silver or on transparent conductive oxides (TCO),
the emissivity and electrical resistivity of which are lowered
following heat treatments. Photocatalytic layers based on titanium
oxide are also more active after heat treatment, as the latter
promotes crystal growth. Heat treatments also make it possible to
create porosity in silica-based layers in order to lower their
light reflection factor.
[0003] Application WO 2010/139908 discloses a heat treatment method
using radiation, in particular infrared laser radiation, focused on
the layer. Such a treatment allows the layer to be heated very
quickly without significantly heating the substrate. Typically, the
temperature at any point on the side of the substrate opposite the
side carrying the layer does not exceed 150.degree. C., or even
100.degree. C., during the treatment. Other types of radiation,
such as that from flash lamps, can also be used for the same
purpose.
[0004] Some layers, however, absorb very little infrared radiation,
so that most of the radiation energy passes through the material
without significantly heating it. To overcome this, it has been
proposed to add a radiation-absorbent layer to the coating to be
treated.
[0005] In order to enable high-speed processing of wide substrates,
such as jumbo-sized (6 m.times.3 m) flat glass sheets from float
processes, it is necessary to have very long (>3 m) laser lines
available. However, it is difficult in practice to ensure stable
power over the entire line and over time. Over- and/or
under-intensities of power along the laser line cause treatment
inhomogeneities of the parts of the substrate passing beneath these
areas compared with the rest of the substrate. The same is true of
variations in the width of the laser line. Treatment
inhomogeneities can also be caused by conveyor systems due to an
irregular travel speed or to vibrations that cause the position of
the substrate to vary with respect to the focal plane of the laser.
For some layers, these treatment inhomogeneities may be sufficient
to cause visible defects on the final product (in particular
optical transmission variation creating a lineage in the direction
of travel or perpendicular thereto). An identical phenomenon can
appear when large-size substrates are treated using flash lamps, in
particular in the overlapping of treatment areas.
[0006] On the other hand, variations in the conveying of the
substrate, for example in the conveying speed or the position of
the substrate with respect to the radiation source, can also cause
the amount of energy impacting the coating to vary and thus affect
treatment homogeneity.
[0007] The present invention proposes to further improve this
process by the use of a layer which largely absorbs radiation and
allows only a negligible amount of it to pass through.
[0008] The subject matter of the present invention is therefore a
process for obtaining a material comprising a substrate coated on
one of its sides with a coating comprising a functional layer, said
process comprising: [0009] a step of depositing the functional
layer on the substrate, then [0010] a step of depositing an
absorbent layer on top of said functional layer, then [0011] a step
of heat treatment by radiation means, said radiation having at
least one treatment wavelength comprised between 200 and 2500 nm,
said absorbent layer being in contact with air during this heat
treatment step, characterized in that the absorbent layer absorbs
at least 80% of the radiation used during the heat treatment and
transmits less than 10% thereof.
[0012] The subject matter of the present invention is therefore a
process for obtaining a material comprising a substrate coated on
one of its sides with a coating comprising a functional layer, said
process comprising: [0013] a step of depositing the functional
layer on the substrate, then [0014] a step of depositing an
absorbent layer on top of said functional layer, then [0015] a step
of heat treatment by radiation means, said radiation having at
least one treatment wavelength comprised between 200 and 2500 nm,
said absorbent layer being in contact with air during this heat
treatment step, characterized in that the absorbent layer has an
absorption/transmission ratio of the radiation used during the heat
treatment greater than 8.
[0016] The present invention also has as its subject matter a
process for obtaining a material comprising a substrate coated on
one of its sides with a coating comprising a functional layer, said
process comprising: [0017] a step of depositing the functional
layer on the substrate, then [0018] a step of depositing an
absorbent layer on top of said functional layer, then [0019] a step
of heat treatment by radiation means, said radiation having at
least one treatment wavelength comprised between 200 and 2500 nm,
said absorbent layer being in contact with air during this heat
treatment step, characterized in that the absorbent layer comprises
at least 5%, preferably at least 10%, more preferentially at least
30%, indeed at least 50%, or even at least 60%, by weight of carbon
particles.
[0020] Another subject matter of the invention is a material
comprising a substrate coated on at least one of its sides with a
coating comprising a functional layer and an absorbent layer
located above the functional layer, characterized in that the
absorbent layer comprises at least 5%, preferably at least 10%,
more preferentially at least 30%, indeed least 50%, or even at
least 60%, by weight of carbon particles. This material corresponds
to an intermediate material of the process according to the
invention, the absorbent layer generally being removed at the end
of the heat treatment or after subsequent storage.
[0021] All the features or all the embodiments described below
apply to both the process and the material according to the
invention.
[0022] Absorption is defined as being equal to the value of 100%
minus the transmission and reflection (spectral and diffuse) of the
layer. It can in a known way be deduced from measurements made with
a spectrophotometer equipped with an integrating sphere. The
absorbent layer absorbs at least 80%, preferably at least 85%, or
even at least 90% of the radiation used during the heat treatment.
Most of the energy of the radiation is thus absorbed by the
absorbent layer and transferred to the coating, in particular the
functional layer, by thermal diffusion. The absorbent layer allows
only a negligible amount of the radiation to pass through. The
absorbent layer typically transmits less than 10%, or even less
than 5% or even less than 1% of the radiation). The rest of the
coating, in particular the functional layer, is thus directly
impacted by only a negligible portion of the radiation, which has
the effect of greatly reducing the sensitivity of the coating to
treatment inhomogeneities. Without wishing to be bound to any
theory, it seems that, by a process of absorption-diffusion of
energy, the absorbent layer according to the invention allows a
more homogeneous distribution of energy to the coating compared
with known processes in which, even in the presence of absorbent
layers, a non-negligible portion of the radiation directly impacts
the coating. The result is an attenuation or even elimination of
defects, in particular optical defects, attributed to treatment
inhomogeneities due to variations in the power density of the
radiation and/or irregularities in the conveying of the substrate.
The improved tolerance with respect to treatment inhomogeneities
obtained using the process according to the invention also makes it
possible to lower the requirements for optical and/or conveying
systems, thereby reducing investment and maintenance costs.
[0023] The substrate is preferably a sheet of glass, of
glass-ceramic, or of an organic polymeric material. It is
preferably transparent, colorless (in which case it can be clear or
extra-clear glass) or colored, for example blue, green, gray or
bronze. The glass is preferably soda-lime-silica type glass, but it
can also be borosilicate or alumino-borosilicate type glass, in
particular for high-temperature applications (oven doors, fireplace
inserts, fire-resistant glazing). The preferred polymeric organic
materials are polycarbonate or poly(methyl methacrylate) or
polyethylene terephthalate (PET). The substrate advantageously has
at least one dimension greater than or equal to 1 m, or even 2 m or
3 m. The thickness of the substrate generally varies between 0.5 mm
and 19 mm, preferably between 0.7 and 9 mm, in particular between 1
and 8 mm, or even between 4 and 6 mm. The substrate can be flat or
curved, or even flexible.
[0024] The glass substrate is preferably of the float type, i.e. it
was obtainable by a process consisting of pouring the molten glass
onto a bath of molten tin (called a float bath). In this case, the
layer to be treated can be deposited on the tin side as well as on
the atmosphere side of the substrate. The "atmosphere" and "tin"
sides are understood to be the sides of the substrate which have
been in contact with the atmosphere in the float bath and in
contact with the molten tin, respectively. The tin side contains a
small surface amount of tin that has diffused into the glass
structure. The glass substrate can also be obtained by lamination
between two rollers, a technique which makes it possible in
particular to print patterns on the surface of the glass.
[0025] Clear glass is understood to mean soda-lime-silica glass
obtained by floatation, not coated with layers, and having a light
transmission of the order of 90%, a light reflection of the order
of 8% and an energy transmission of the order of 83% for a
thickness of 4 mm. The light and energy transmissions and
reflections are as defined by standard NF EN 410. Typical clear
glasses are for example marketed under the name SGG Planilux by the
firm Saint-Gobain Glass France or under the name Planibel Clair by
the firm AGC Flat Glass Europe. These substrates are typically used
for the manufacture of low-emissivity glass.
[0026] The functional layer, and possibly all the layers deposited
on or under it, are typically thin layers, in the sense that their
thickness is typically from 0.5 nm to 10 .mu.m, more generally from
1 nm to 1 .mu.m. "Thickness" means physical thickness throughout
the present text.
[0027] The functional layer and the absorbent layer are preferably
deposited on at least 90% of the substrate surface. In certain
embodiments, the absorbent layer can however be deposited on only
part of the substrate surface, in particular on a peripheral
region, on a central region, or so as to create a pattern, for
example a periodic pattern or a logo.
[0028] In the present application, the terms "under" or "below" and
"over" or "above", associated with the position of a first layer
relative to a second layer, mean that the first layer is closer to,
or more distant from, the substrate than the second layer. However,
these terms do not exclude the presence of other layers between
said first and second layers. On the contrary, a first layer "in
direct contact" with a second layer means that no other layer is
disposed between them. The same is true of the terms "directly on"
or "directly above" and "directly under" or "directly below". Thus,
it is understood that, unless otherwise indicated, other layers may
be interposed between each layer in the stack.
[0029] Throughout the text, "based on" is understood to mean that a
layer generally comprises at least 50% by weight of the element
considered (metal, oxide, etc.), preferably at least 60% and even
70% or 80%, or even 90%, 95% or 99% by weight of that element. In
certain cases, the layer consists of this element, except for
impurities.
[0030] The functional layer preferably provides the coated
substrate with at least one functionality selected from low
emissivity, low electrical resistivity, anti-reflective effect,
self-cleaning or easy cleaning.
[0031] Preferably the functional layer is selected from layers
based on a metal, in particular silver, layers based on titanium
oxide, layers based on silica or layers based on a transparent,
electrically-conductive oxide.
[0032] The functional layer may be the only layer deposited on the
substrate (in addition to the absorbent layer). Alternatively, the
functional layer can be comprised in a stack of thin films. A
"coating" is defined as the assembly comprising the functional
layer(s), the absorbent layer and, if need be, any other layer
deposited on the same side of the substrate. The coating may
comprise a plurality of functional layers, in particular two,
three, or four functional layers.
[0033] The thickness of the or each functional layer is typically
comprised between 1 nm and 5 .mu.m, in particular between 2 nm and
2 .mu.m, more particularly between 10 nm and 1 .mu.m.
[0034] According to a preferred embodiment, the functional layer is
based on a metal, typically silver or even gold, molybdenum or
niobium. The functional layer preferably consists of this metal.
Such metals have low emissivity and low electrical resistivity
properties, so that the coated substrates can be used for the
manufacture of heat-insulating glazing, heated glazing or
electrodes. The thickness of the functional layer is then
preferably comprised in the range from 2 to 20 nm.
[0035] In this embodiment, the coating comprises at least one
metallic functional layer, for example one, two or three functional
layers, each generally being disposed between at least two
dielectric layers, typically layers of oxide, nitride or
oxynitride, for example layers of silicon nitride, zinc oxide
and/or tin oxide, titanium oxide etc. This type of coating is
preferably deposited entirely by cathode sputtering, in particular
assisted by a magnetic field (magnetron process)--with the possible
exception of the absorbent layer.
[0036] According to another preferred embodiment, the functional
layer is a layer based on titanium oxide, in particular a layer
consisting or essentially consisting of titanium oxide.
[0037] Thin films based on titanium oxide have the distinctive
feature of being self-cleaning, facilitating the degradation of
organic compounds under the action of ultraviolet radiation
(photocatalysis phenomenon) and the removal of mineral dirt (dust)
under the action of a stream of water. Titanium dioxide
crystallized in the anatase form is much more effective in terms of
degradation of organic compounds than amorphous titanium dioxide or
titanium dioxide crystallized in the rutile or brookite form.
Titanium oxide can optionally be doped with a metal ion, for
example a transition metal ion, or with nitrogen, carbon, fluorine,
etc. atoms. Titanium oxide can also be sub-stoichiometric or
over-stoichiometric in oxygen (TiO.sub.2 or TiO.sub.x).
[0038] The layer based on titanium oxide is preferably deposited by
magnetron cathode sputtering. However, this technique does not
produce very active layers, as the titanium oxide they contain is
crystallized little if at all. Heat treatment is then necessary to
give appreciable self-cleaning properties. In order to improve
these properties, it is preferable, particularly when the substrate
is intended to undergo a prolonged heat treatment, for example a
quenching or curving treatment, to insert between the substrate and
the titanium oxide layer at least one alkali migration barrier
layer, selected in particular from the layers based on silica,
silicon oxycarbide, alumina, silicon nitride.
[0039] According to another preferred embodiment, the functional
layer is a layer based on a transparent, electrically-conductive
oxide. The transparent, electrically-conductive oxide is preferably
selected from indium tin oxide (ITO) layers, aluminum- or
gallium-doped zinc oxide layers and fluorine- or antimony-doped tin
oxide layers.
[0040] This type of layer provides properties of electrical
conduction but also of low emissivity, allowing the material to be
used in the manufacture of insulating glass units,
anti-condensation glass units, or electrodes, for example for
photovoltaic cells, display screens or lighting devices.
[0041] According to yet another preferred embodiment, the
functional layer is a silica-based layer. This type of layer
absorbs little in the wavelength range considered, in particular in
the near infrared range, so that in the absence of an absorbent
layer the heat treatment is ineffective.
[0042] The silica-based layer is preferably, after heat treatment,
essentially made up or even made up of silica. The silica-based
layer is advantageously anti-reflective, in the sense that the
light reflection factor on the layer side is at most 6%, in
particular 5% after heat treatment, when the layer is deposited on
only one side of a glass substrate (the value therefore takes into
account the reflection of the opposite uncoated side, which is
about 4%).
[0043] According to a first variant, the silica-based layer
comprises, prior to heat treatment, silicon, oxygen, carbon and
optionally hydrogen, the latter two elements being at least
partially removed during the heat treatment so as to obtain a
porous layer essentially consisting of silica. This layer is
preferentially deposited by magnetron cathode sputtering of a
silicon or silica target or by plasma-assisted chemical vapor
deposition using an organometallic compound such as
hexamethyldisiloxane as silicon precursor.
[0044] According to a second variant, the silica-based layer
comprises, prior to heat treatment, a silica matrix and
pore-forming agents, the latter being removed during the heat
treatment so as to obtain a porous layer essentially consisting of
silica. The pore-forming agents are preferably organic, in
particular polymeric, for example poly(methyl methacrylate), the
average size of the pore-forming agents preferably being comprised
in the range from 20 to 200 nm. This layer is preferentially
deposited by a sol-gel type process.
[0045] The functional layer can be obtained by any type of
thin-film deposition process. These may for example be processes
such as sol-gel, pyrolysis (liquid or solid), chemical vapor
deposition (CVD), in particular plasma-assisted chemical vapor
deposition (APCVD), optionally under atmospheric pressure
(APPECVD), evaporation, cathode sputtering, in particular assisted
by a magnetic field (magnetron process). In the latter process, a
plasma is created under a high vacuum in the vicinity of a target
containing the chemical elements to be deposited. The active
species of the plasma, by bombarding the target, tear off said
elements, which are deposited on the substrate forming the desired
thin film. This process is said to be "reactive" when the layer
consists of a material resulting from a chemical reaction between
the elements torn from the target and the gas contained in the
plasma. The major advantage of this process lies in the possibility
of depositing on the same line a very complex stack of layers by
successively running the substrate under different targets,
generally in one and the same device. It is thus possible to obtain
in this way the complete stack, containing the absorbent layer if
need be.
[0046] The absorbent layer typically includes an agent that absorbs
at the wavelengths of the radiation. It is preferably in the form
of particles. The absorbing agent can be any inorganic or organic
pigment that absorbs at the wavelengths of the radiation. Examples
of organic pigments include bitumen, perylenes such as perylene
black, perylene red, perylene burgundy, quinacridones such as
quinacridone magenta, quinacridone red, phthalocyanines such as
copper phthalocyanine, brominated copper phthalocyanine, azocarbons
such as methyl orange, phenylazophenol, tartrazine, carbonaceous
particles such as carbon black or graphite. Examples of mineral
pigments include metal oxides such as iron oxide, manganese oxide,
titanium dioxide, zinc oxide, metal sulfides such as sodium
sulfide, cadmium sulfide or mercury sulfide. The amount of
absorbing agent in the absorbent layer as well as the thickness of
the absorbent layer must be adapted according to the nature of the
absorbing agent to obtain an absorbent layer according to the
invention absorbing at least 80% of the radiation.
[0047] The absorbing agent is preferably selected from carbon
particles. They indeed have the advantage of having a wide
absorption spectrum. Absorbent layers comprising carbon particles
can therefore be adapted to radiation sources emitting in different
wavelengths. The carbon particles can be selected from carbon
black, graphite, graphene, carbon nanotubes, or mixtures thereof.
However, carbon black particles are preferred for economic reasons
in particular. Carbon particles typically have an average size of
100 to 1500 nm, preferably 150 to 1200 nm. The particle size is
determined by dynamic light scattering.
[0048] The absorbent layer preferably comprises at least 5%, more
preferentially at least 8%, or even at least 10%, by weight of
absorbing agent. In a particular embodiment, the absorbent layer
may be mainly based on absorbing agent, i.e. it may comprise at
least 50%, preferably at least 60%, by weight of absorbing agent.
It may comprise up to 90% or even 80% by weight of absorbing
agent.
[0049] The absorbent layer typically has a thickness of 0.5 .mu.m,
or even 0.7 .mu.m, 0.8 .mu.m, or even 0.8 .mu.m, to 50 .mu.m, or
even 20 .mu.m, 10 .mu.m, or even 5 .mu.m.
[0050] In a first embodiment, the absorbent layer comprises an
absorbing agent dispersed in an organic matrix. The organic matrix
may be based on polymers which are water-soluble, water-dispersible
and/or can be at least partially removed by thermal decomposition
during the heat treatment according to the invention. In this
embodiment, the absorbent layer typically has a thickness of 1 to
50 .mu.m, preferably 2 to 30 .mu.m, or even 3 to 10 .mu.m.
[0051] Examples of suitable organic matrices include polymers
comprising one or more homopolymers or copolymers of starch,
casein, acrylates, acrylamide, glycols such as ethylene glycol,
vinyl acetate, vinyl alcohol, vinylpyrrolidone, styrene/acrylic
acid copolymers, ethylene/acrylic acid copolymers, cellulose or
derivatives thereof such as methylcellulose, ethylcellulose,
hydroxypropylmethylcellulose or carboxymethylcellulose.
[0052] In a first variant, the organic matrix is soluble and/or
dispersible in water. The absorbent layer can then be obtained from
a coating solution, preferably water-based, comprising a
water-soluble or water-dispersible film-forming polymer, preferably
based on vinyl alcohol, and an absorbing agent. The coating
solution typically comprises up to 30% by weight, preferably up to
24% by weight, or even 5 to 12% by weight, of film-forming polymer
based on the total weight of the solution. The amount of absorbing
agent in the coating solution is determined according to the
desired amount in the absorbent layer. It is typically 5% to 20% by
weight based on the total weight of dry matter. The coating
solution may also comprise conventional additives such as
surfactants, rheological agents, defoaming agents, or mineral
fillers.
[0053] The coating solution can be deposited on the coated
substrate by any conventional liquid deposition method such as
spray coating, flow coating, curtain coating or roller coating. It
may also be deposited by printing methods such as inkjet printing,
flexography or screen printing, in particular for obtaining
patterns.
[0054] In a second variant, the organic matrix is neither soluble
or nor dispersible in water. In this case, the organic matrix is
preferably based on acrylate polymer. The absorbent layer is then
typically obtained from a liquid composition comprising
(meth)acrylate compounds, preferably selected from monomers,
oligomers, prepolymers or polymers comprising at least one
(meth)acrylate function. The liquid composition, preferably
essentially solvent-free, can be deposited on the coated substrate
by any conventional liquid-phase deposition method, in particular
by roller coating. It can then be polymerized, preferably by UV
irradiation, by firing or by electron-beam bombardment.
[0055] "(Meth) acrylate" means acrylate or methacrylate equivalent.
"(Meth)acrylate compounds" means esters of acrylic or methacrylic
acid with at least one acroyl (CH2=CH--CO--) or methacroyl
(CH2=CH(CH3)-CO--) function. These esters may be monomers,
oligomers, pre-polymers or polymers. The (meth)acrylate compounds
used may be monofunctional or polyfunctional (meth)acrylates,
including di-, tri-, tetra-, penta- or hexa-functional
(meth)acrylates. Examples of such compounds are: monofunctional
(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate,
n- or tert-butyl(meth)acrylate, hexyl(meth)acrylate,
cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,
benzyl(meth)acrylate, 2-ethoxyethyl(meth)acrylate,
phenyloxyethyl(meth)acrylate, hydroxyethylacrylate,
hydroxypropyl(meth)acrylate, vinyl(meth)acrylate caprolactone
acrylate, isobornyl methacrylate, lauryl methacrylate,
polypropylene glycol monomethacrylate, [0056] difunctional
(meth)acrylates such as 1,4-butanediol di(meth)acrylate, ethylene
dimethacrylate, 1,6-hexandiol di(meth)acrylate, bisphenol A
di(meth)acrylate, trimethylolpropane diacrylate, triethylene glycol
diacrylate, ethylene glycol di(meth)acrylate, polyethylene glycol
di(meth)acrylate, tricyclodecane dimethanol diacrylate, [0057]
trifunctional (meth)acrylates such as trimethylolpropane
trimethacrylate, trimethylolpropane triacrylate, pentaerythritol
triacrylate, ethoxylated trimethylolpropane triacrylate,
trimethylolpropane trimethacrylate, tripropylene glycol
triacrylate, [0058] higher functionality (meth)acrylates such as
pentaerythritol tetra(meth)acrylate, ditrimethylpropane
tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate or
hexa(meth)acrylate.
[0059] In addition to the (meth)acrylate compounds, the liquid
composition comprises an amount of absorbing agent corresponding to
the desired amount in the absorbent layer. It is typically 5% to
20% by weight of the total weight. The liquid composition further
comprises a polymerization initiator, the nature of which depends
on the type of polymerization selected. For example, in the case of
thermal polymerization, initiators of the benzoyl peroxide type are
used. In the case of curing by UV radiation, so-called
photoinitiators are used. The liquid composition may comprise other
additives such as mineral fillers or rheological agents. According
to an advantageous embodiment, the temporary protective layer does
not contain any mineral fillers other than carbon black, nor
additives that cannot be removed during heat treatment, such as
organic compounds containing silicon of the siloxane type.
[0060] In a second embodiment, the absorbent layer consists mainly
of the absorbing agent, i.e. it typically comprises 50-90% by
weight of absorbing agent. In this case, the absorbent layer is
generally obtained from a suspension of absorbing agent in a
solvent (in particular alcoholic, aqueous or a water-alcohol
mixture), optionally with the addition of surfactants. The
suspension typically comprises 1 to 10% by weight of absorbing
agent. The suspension can be deposited on the coated substrate by
any conventional liquid deposition method such as spray coating,
flow coating, curtain coating or roller coating. It may also be
deposited by printing methods such as inkjet printing, flexography
or screen printing, in particular for the obtaining of patterns.
The deposit is then dried to remove the solvent and obtain an
absorbent layer typically having a thickness of 0.5 to 5 .mu.m,
preferably 0.7 to 4 .mu.m, or even 0.8 to 3 .mu.m.
[0061] The absorbent layer is in contact with an oxidizing
atmosphere, generally air, during the heat treatment step according
to the invention. In other words, the absorbent layer constitutes
the last layer of the coating. In particular, in the case of a
plurality of functional layers, the absorbent layer is located
above the functional layer furthest from the substrate.
[0062] During the heat treatment according to the invention, the
radiation is largely absorbed by the absorbent layer and the
absorbed energy is returned by diffusion to the rest of the
coating, thus allowing the coating to be cured without significant
direct impact of the coating, in particular the functional layer,
by the radiation.
[0063] After the heat treatment step the absorbent layer can be
easily removed by washing with a solvent, preferably water. Indeed,
even in the case of an absorbent layer based on an organic matrix
which is insoluble or dispersible in water, the heat treatment has
the effect of at least partially decomposing said matrix, thus
allowing the residues to be removed by simple washing.
[0064] Regardless of the embodiment, the use of carbon particles as
an absorbing agent is advantageous, as these can be partially
removed during the heat treatment according to the invention. Thus,
the higher the proportion of carbon particles in the absorbent
layer, the more easily the residue of the absorbent layer after
heat treatment can be removed. Moreover, in the case of a layer
mainly based on carbon particles, the combination of a high
concentration of carbon particles combined with the strong
absorption properties of these particles makes it possible to
obtain very absorbent and relatively thin layers, promoting heat
exchanges with the coating, and consequently the efficiency of the
treatment. Absorbent layers mainly based on carbon particles are
preferred for these reasons.
[0065] During heat treatment, the radiation is preferably selected
from laser radiation, radiation from at least one infrared lamp, or
radiation from at least one flash lamp.
[0066] According to a first preferred embodiment, the radiation
comes from at least one flash lamp.
[0067] Such lamps are usually in the form of sealed glass or quartz
tubes filled with a noble gas and fitted with electrodes at their
ends. A short electrical pulse, obtained by discharging a
capacitor, causes the gas to ionize and produce a particularly
intense, incoherent light. The emission spectrum generally
comprises at least two emission lines, preferably a continuous
spectrum with a maximum emission in the near ultraviolet and
extending to the near infrared. In this case, the heat treatment
uses a continuum of treatment wavelengths.
[0068] The lamp is preferably a xenon lamp. It can also be an
argon, helium or krypton lamp. The emission spectrum preferably
comprises several lines, in particular at wavelengths ranging from
160 to 1000 nm.
[0069] The flash duration is preferably comprised in the range from
0.05 to 20 milliseconds, in particular from 0.1 to 5 milliseconds.
The repetition rate is preferably comprised in the range from 0.1
to 5 Hz, in particular from 0.2 to 2 Hz.
[0070] The radiation can be from several lamps disposed side by
side, for example 5 to 20 lamps, or even 8 to 15 lamps, so that a
larger area can be treated simultaneously. In this case, all the
lamps can emit flashes simultaneously.
[0071] The or each lamp is preferably disposed transversely to the
longer sides of the substrate. The or each lamp preferably has a
length of at least 1 m, in particular 2 m and even 3 m, so that
large substrates can be treated. The use of an absorbent layer
according to the invention nevertheless makes it possible to use
modules of shorter lengths combined with each other to achieve the
desired length without, however, affecting the homogeneity of the
treatment generally induced by the overlapping areas between the
irradiation areas of each module.
[0072] The capacitor is typically charged to a voltage of 500 V to
500 kV. The current density is preferably at least 4000 A/cm.sup.2.
The total energy density emitted by the flash lamps, relative to
the surface of the coating, is preferably comprised between 1 and
100 J/cm.sup.2, in particular between 1 and 30 J/cm.sup.2, or even
between 5 and 20 J/cm.sup.2.
[0073] According to a second preferred embodiment, the radiation is
laser radiation, in particular laser radiation in the form of at
least one laser line, preferably focused on the absorbent
layer.
[0074] Laser radiation is preferably generated by modules
comprising one or more laser sources as well as shaping and
redirecting optics.
[0075] The laser sources are typically laser diodes or fiber
lasers, including fiber, diode or disk lasers. Laser diodes allow
high power densities to be achieved economically in relation to the
electrical power supply, with a small footprint. Fiber lasers are
even more compact, and the linear power obtained can be even
higher, but at a higher cost. Fiber lasers are defined as lasers in
which the place of generation of the laser light is spatially
offset from the place of delivery, the laser light being delivered
by means of at least one optical fiber. In the case of a disk
laser, the laser light is generated in a resonant cavity in which
the emitting medium is located which is in the form of a disk, for
example a thin disk (about 0.1 mm thick) of Yb:YAG. The light thus
generated is coupled into at least one optical fiber directed
towards the treatment site. The laser can also be fiber-based, in
the sense that the amplification medium is itself an optical fiber.
Fiber or disk lasers are preferably optically pumped using laser
diodes. The radiation from the laser sources is preferably
continuous. Alternatively, it can be pulsed.
[0076] The wavelength of the laser radiation, thus the treatment
wavelength, is preferably comprised in the range from 200 to 2500
nm, preferably 500 to 1300 nm, in particular from 800 to 1100 nm.
Power laser diodes emitting at one or more wavelengths selected
from 808 nm, 880 nm, 915 nm, 940 nm or 980 nm have proven to be
particularly suitable. In the case of a disk laser, the treatment
wavelength is for example 1030 nm (emission wavelength for a Yb:YAG
laser). For a fiber laser, the treatment wavelength is typically
1070 nm.
[0077] The number of laser lines and their disposition are
advantageously selected so that the entire width of the substrate
is treated.
[0078] Several disjointed lines can be used, for example in a
staggered or bird's-eye arrangement. In general, however, the laser
lines are combined to form a single laser line. In the case of
narrow substrates, this laser line can be generated by a single
laser module. On the other hand, in the case of large substrate
widths, for example greater than 1 m, or 2 m and even 3 m, the
laser line results advantageously from the combination of a
plurality of elementary laser lines, each generated by independent
laser modules. The length of these elementary laser lines typically
ranges from 10 to 100 cm, in particular from 30 to 75 cm, or even
from 30 to 60 cm. The elementary lines are preferably disposed in
such a way that they partially overlap in the longitudinal
direction and preferably have an offset in the width direction,
said offset being less than half the sum of the widths of two
adjacent elementary lines.
[0079] "Length" means the longest dimension of the line, measured
on the surface of the coating in a first direction, and "width"
means the dimension in the second direction, perpendicular to the
first direction. As is customary in the field of lasers, the width
w of the line corresponds to the distance (in this second
direction) between the beam axis (where the radiation intensity is
maximum) and the point where the radiation intensity is 1/e.sup.2
times the maximum intensity. If the longitudinal axis of the laser
line is named x, a width distribution along this axis, named w(x),
can be defined.
[0080] The average width of the or each laser line is preferably at
least 35 .mu.m, preferably comprised in the range from 40 to 100
.mu.m, or even from 40 to 70 .mu.m, or in the range from 110 .mu.m
to 30 mm. Throughout the present text "average" means the
arithmetic average. Over the entire length of the line, the
distribution of widths is preferably narrow in order to maximally
limit any heterogeneity of treatment. Thus, the difference between
the largest and smallest width is preferably no more than 10% of
the value of the average width. This figure should preferably be at
most 5% and even 3%. In certain embodiments this difference can be
greater than 10%, for example from 11 to 20%.
[0081] The linear power of the laser line is preferably at least 50
W/cm, advantageously 100 or 150 W/cm, in particular 200 W/cm, or
even 300 W/cm and even 350 W/cm. It is even advantageously at least
400 W/cm, in particular 500 W/cm, or even 600, 800 or 1000 W/cm.
Linear power is measured at the point where the or each laser line
is focused on the coating. It can be measured by placing a power
detector along the line, for example a calorimeter power meter,
such as the Beam Finder S/N 2000716 from the firm Coherent Inc. The
power is advantageously distributed homogeneously along the entire
length of the or each line. Preferably, the difference between the
highest and lowest power is less than 10% of the average power.
[0082] The absorbent layer according to the invention is suitable
for laser treatment and has at least one of the following
characteristics 1 to 3 or combinations thereof, in particular 1+2,
1+3 or 1+2+3:
1--an average line width of 110 .mu.m to 30 mm; 2--a line power of
50 to 290 W/cm; 3--a difference between the largest and the
smallest width of 11% to 20% of the value of the average width.
[0083] According to a third preferred embodiment, the radiation is
radiation from one or more infrared lamps. The one or more infrared
lamps preferably have a power of 50 to 150 W/m.sup.2. Their
emission spectrum typically has at least 80% of the intensity
between 400 and 1500 nm with a maximum between 800 and 1000 nm.
[0084] In order to treat the entire surface of the substrate, a
relative displacement between the radiation source and said
substrate is preferably created. Preferably, in particular for
large-size substrates, the or each radiation source (in particular
laser line or flash lamp) is fixed, and the substrate is in motion,
so that the relative displacement speeds will correspond to the
running speed of the substrate. Preferably, the or each laser line
is substantially perpendicular to the direction of movement.
[0085] The process according to the invention has the advantage of
heating only the coating, without significant heating of the entire
substrate. This eliminates the need for slow and controlled cooling
of the substrate before cutting or storage. During the entire heat
treatment step, the temperature at any point on the side of the
substrate opposite that bearing the functional layer is preferably
at most 150.degree. C., in particular 100.degree. C. and even
50.degree. C.
[0086] The maximum temperature to which each point of the coating
is subjected during heat treatment is preferably at least
300.degree. C., in particular 350.degree. C., or even 400.degree.
C., and even 500.degree. C. or 600.degree. C., and preferably less
than 800.degree. C., or even less than 700.degree. C. The maximum
temperature is in particular experienced at the moment when the
point of the coating in question passes below the laser line or is
irradiated by the flash lamp. At any given moment, only those
points on the surface of the coating which are below the laser line
or under the flash lamp and in its immediate vicinity (for example
within 1 millimeter) are normally at a temperature of at least
300.degree. C. For distances to the laser line (measured in the
direction of travel) greater than 2 mm, in particular 5 mm,
including downstream of the laser line, the temperature of the
coating is normally at most 50.degree. C., and even 40.degree. C.
or 30.degree. C.
[0087] Each point of the coating undergoes the heat treatment (or
is brought to the maximum temperature) for a period of time
advantageously comprised in the range from 0.05 to 10 ms, in
particular from 0.1 to 5 ms, or from 0.1 to 2 ms. In the case of
treatment by means of a laser line, this duration is determined
both by the width of the laser line and by the relative speed of
movement between the substrate and the laser line. In the case of
treatment by means of a flash lamp, this time corresponds to the
duration of the flash.
[0088] The substrate can be set in motion by any mechanical
conveying means, for example by means of belts, rollers,
translating plates. The conveying system allows the speed of the
movement to be controlled and regulated. If the substrate is made
of flexible organic polymeric material, the movement can be carried
out by means of a film feed system in the form of a succession of
rollers.
[0089] All relative positions of the substrate and the laser are of
course possible, as long as the substrate surface can be properly
irradiated. The substrate will most often be disposed horizontally,
but it can also be disposed vertically, or at any possible
inclination. When the substrate is disposed horizontally, the
treatment device is generally disposed to irradiate the upper side
of the substrate. The treatment device may also irradiate the
underside of the substrate. In this case, the substrate support
system, and optionally the substrate conveying system when the
substrate is in motion, must allow radiation to pass through the
area to be irradiated. This is the case, for example, when using
laser radiation and conveyor rollers: since the rollers are set
apart, it is possible to arrange the laser in an area between two
successive rollers.
[0090] The speed of the relative displacement movement between the
substrate and the or each radiation source (including the or each
laser line) is advantageously at least 2 m/min, in particular 5
m/min and even 6 m/min or 7 m/min, or 8 m/min and even 9 m/min or
10 m/min. This can be adjusted according to the nature of the
functional layer to be treated and the power of the radiation
source used.
[0091] The heat treatment device can be integrated into a layer
deposition line, for example a magnetic field assisted sputtering
deposition line (magnetron process), or a chemical vapor deposition
(CVD) line, such as plasma assisted chemical vapor deposition
(PECVD), vacuum or atmospheric pressure chemical vapor deposition
(APPECVD). The line typically comprises substrate handling devices,
a deposition facility, optical control devices, stacking devices.
The substrates, in particular glass substrates, are passed, for
example on conveyor rollers, successively in front of each device
or each installation.
[0092] The heat treatment device is preferably located immediately
after the coating deposition installation, for example at the
outlet of the deposition installation. The coated substrate can
thus be treated in-line after the coating has been deposited, at
the exit of the deposition installation and before the optical
control devices, or after the optical control devices and before
the substrate stacking devices.
[0093] The heat treatment device can also be integrated into the
deposition installation. For example, the laser or flash lamp can
be introduced into one of the chambers of a cathode sputtering
deposition installation, in particular into a chamber where the
atmosphere is rarefied, in particular at a pressure comprised
between 10.sup.-6 mbar and 10.sup.-2 mbar. The heat treatment
device can also be disposed outside the deposition installation,
but in such a way as to treat a substrate situated inside said
installation. For this purpose, it is sufficient to provide a
porthole transparent to the wavelength of the radiation used,
through which the radiation would come to treat the layer. It is
thus possible to treat a functional layer (for example a silver
layer) before the subsequent deposition of another layer in the
same installation.
[0094] Whether the heat treatment device is outside or integrated
into the deposition facility, these processes, referred to as
in-line or continuous processes, are preferable to a rework process
in which it would be necessary to stack the glass substrates
between the deposition step and the heat treatment.
[0095] However, rework processes may be of interest in cases where
the heat treatment according to the invention is carried out in a
different place from that in which the deposit is made, for example
in a place where the processing of glass is carried out. The heat
treatment device can therefore be integrated into lines other than
the coating line. It can, for example, be integrated into a
production line for multiple glazing (in particular double or
triple glazing), into a production line for laminated glazing, or
into a production line for curved and/or tempered glazing.
Laminated, curved or tempered glass can be used both as building
and automotive glazing. In these different cases, the heat
treatment according to the invention is preferably carried out
before the multiple or laminated glazing is produced. However, the
heat treatment can be carried out after the double glazing or
laminated glazing has been produced.
[0096] The heat treatment device is preferably disposed in an
enclosed enclosure to ensure personal safety by avoiding any
contact with radiation and to avoid any pollution, in particular of
the substrate, the optics or the treatment area.
[0097] The process according to the invention may thus include a
washing step after the heat treatment step. This washing step
carried out using a solvent, typically water, removes the residue
of the absorbent layer after heat treatment. In a first embodiment,
the washing can take place immediately after the heat treatment
step. In another embodiment, the washing step is not carried out
immediately after the heat treatment step. Indeed, it has been
noticed that the residue of the absorbent layer after heat
treatment can be used as a substitute for the use of a spacer
between the treated substrates during storage. In this case, the
process according to the invention preferably does not include a
washing step between the heat treatment step and subsequent storage
of the substrate. The washing step can be carried out just before
integration operations, for example in a glazing, in particular
after storage and possible transport of the substrates. This is
particularly advantageous when the absorbing agent is selected from
carbon particles. In this case, the absorbent layer residue
includes carbon particles not bound to the substrate, which act as
lubricants when the treated substrates are stacked together.
[0098] The present invention also has as its subject matter a
substrate coated with a coating comprising a functional layer, said
coating being surmounted by an absorbent layer according to the
invention having undergone a heat treatment. Such a treated layer
may comprise, in particular, carbon particles not bonded to the
substrate.
[0099] In the case of a glass substrate, the material obtained by
the process according to the invention may form or be integrated
into a glazing, in particular for building or transport. This may
be, for example, multiple glazing (double, triple, etc.),
monolithic glazing, curved glazing, laminated glazing. In the case
of self-cleaning layer based on titanium oxides, the material can
in particular constitute the first sheet of a multiple glazing, the
functional layer being positioned opposite 1 of said glazing. In
the case of silver-based layers, the functional layer is preferably
positioned inside the multiple glazing.
[0100] The material obtained by the process according to the
invention can further be integrated into a photovoltaic cell. In
the case of anti-reflection silica-based layers as mentioned above,
the material coated with these can form the front side of a
photovoltaic cell.
[0101] The material obtained by the process according to the
invention can further be integrated into a display screen or
lighting device or a photovoltaic cell as a substrate provided with
an electrode.
[0102] The invention is illustrated with the following non-limiting
examples of embodiments.
[0103] All tests are carried out on a glazing formed by a sheet of
Planiclear.RTM. glass with a low-emissivity stack on one of its
sides consisting of the following successive layers (the values in
brackets correspond to the thickness of the layers expressed in
nm):
//TiO.sub.2(24)/ZnO(4)/Ag(13.5)/Ti(0.4)/ZnO(4)/TiO.sub.2(12)/Si.sub.3N.s-
ub.4(30)
[0104] Five samples are prepared (Ex1 and Ex2 according to the
invention, and comparative CEx1, CEx2 and CEx 3) which differ by
the absorbent overlayer deposited before laser treatment.
[0105] For Example 1, an absorbent layer comprising carbon black
particles dispersed in an organic matrix based on an acrylate
polymer was deposited as follows. 7% by weight of carbon black
particles were dispersed in an acrylate polymer suspension. The
suspension was deposited by roller coating and dried at room
temperature.
[0106] For Example 2, a 1 .mu.m layer of carbon black particles was
deposited as follows. 2% by weight of carbon black particles having
an average diameter of 500 nm were dispersed in an aqueous
surfactant solution by means of ultrasonic treatment. The
suspension was deposited with a scraper and dried at room
temperature.
[0107] For Comparative Example 1, a 5 .mu.m layer of a black ink
marketed as LF-140 BLACK by Mimaki Engineering was applied by
roller and dried at room temperature.
[0108] For Comparative Example 2, a 2 nm SnZn metal layer was
deposited by cathode sputtering.
[0109] For Comparative Example 3, a 10 nm carbon layer was
deposited by cathode sputtering.
[0110] The samples were subjected to heat treatment by a laser line
having the following characteristics: wavelength 915 nm and 980 nm;
line length 30 cm; line width at the focal plane 45 .mu.m with a
variation of .+-.10 .mu.m along the line. The running speed of the
substrates, set at 36 m/min, shows a variation of .+-.5% during
processing. The line power of the laser, which has a homogeneity of
.+-.10% along the line, was set so as to obtain a comparable gain
of at least 20% for each of the examples.
[0111] The conductivity gain is defined as the difference between
the initial R.quadrature. (before heat treatment) and the final
R.quadrature. (after heat treatment) relative to the initial
R.quadrature.:
Gain
(%)=(R.quadrature..sub.initial-R.quadrature..sub.final)/R.quadratur-
e..sub.initial
[0112] The table below shows, for each sample, the absorption of
the absorbent layer at the wavelengths of the laser radiation, the
conductivity gain and the visibility of defects due to treatment
inhomogeneities after heat treatment.
[0113] The visibility of defects due to treatment inhomogeneities
is evaluated by an operator with the naked eye according to the
following scoring system:
++: no defects are visible to the naked eye, +: localized defects,
limited to certain areas of the sample, are perceptible to the
naked eye under intense diffuse illumination (>800 lux), -
localized defects limited to certain areas of the sample are
visible to the naked eye under standard illumination (<500 lux),
and --: defects extending over the entire surface of the sample are
perceptible to the naked eye under standard illumination (<500
lux).
TABLE-US-00001 TABLE 1 Ex 1 Ex 2 CEx 1 CEx 2 CEx 3 Absorption of
>80% >90% <50% <30% <20% laser radiation (%) Laser
power 200 150 320 320 320 (W/cm) Gain 22 22 21 20 20 (%) Visibility
of + ++ - - - - - defects
[0114] The five samples have, after heat treatment, approximately
equivalent values of light absorption and resistance per square.
Defects due to treatment inhomogeneities are significantly less
visible for Examples 1 and 2 according to the invention as compared
with the comparative examples.
* * * * *